Analysis of Lysinoalanine and Lanthionine

Ansynth Service B.V. is highly specialized in analysis of lysinoalanine and analysis of lanthionine as indicators of quality of feed and food products.

Although lysinoalanine (LAL) and lanthionine (LAN) are not part of or related to the Maillard Reaction Products, their presence give rise to similar unwanted nutritional effects like a reduction of protein digestibility and availability of (essential) amino acids and possible toxic side effects.

The mechanism of the formation of lysinoalanine N6-(DL-2-amino-2-carboxyethyl)-L-lysine is a 2 step process.
The first step involves hydroxide ion-catalyzed formation of a dehydroalanine (DHA) intermediate by β-elimination (dehydration) from serine residues and elimination of H2S from cysteine residues. This reaction is pH dependent and accelerates under strong alkaline conditions.
Dehydroalanine as intermediate is also found in food proteins including casein) that have been heated and/or treated with an alkali such as sodium hydroxide.
Dehydroalanine containing proteins also occur naturally for instance like in protein antibiotics such as epidermin and nisine (food preservative). These peptides are toxic or antibiotic and constitute parts of lantibiotics or microcystins.

In the second step dehydroalanine serves as an intermediate for multiple possible reactions such as:

Formation of lysinoalanine, when the double bond of dehydroalanine reacts with the ε-aminogroup of lysine.

Formation of lanthionine, when dehydroalanine reacts with cysteine.

Formation of hystidylalanine, when reaction of dehydroalanine with histidine takes place.

Formation of ornithinoalinine, when reaction with ornithine takes place.

The optimal conditions for formation of lysinoalanine include a high pH, elevated temperature and increased exposure time.

Lysinoalanine is especially found in alkali treated proteins such as casein and soy proteins, but also found in proteins of home-cooked and commercially available foods.

Lanthionine is especially found in cysteine rich materials such as hair, wool, feathers but also lactalbumine. Such materials, rich in –SH containing group, (cysteine, n-acetyl-cysteine and glutathione), minimize the formation of lysinoalanine but induce the formation of lanthionine.